My invention relates to friction hinges, and, more particularly, to friction hinges for applications demanding an angularly dependent torque.
U.S. Pat. No. 4,630,333 reveals a friction hinge that is adjustable for holding a door or a lid in a particular angular position. The adjustment permits the user to set the hinge, within a certain range, to any desired, constant torque.
U.S. patent application Ser. No. 07/613,025, filed Nov. 14, 1990, reveals a friction hinge capable of providing a different, preset amount of torque for each direction of rotation. This device has, for each direction, a band that provides a presetable, constant slip torque that depends upon the force applied to the tail of the band.
None of the friction hinges revealed in the prior art provides adequately for the problem of a torque requirement that changes with the angle at which the hinge is deployed. Such commonplace items as display cases, briefcases, and portable computer screens have lids which can advantageously be positioned at an angle and held there, the desired angle varying from time to time. The torque needed to maintain the position of such a lid varies as the cosine of the angle between the lid and a horizontal line. If sufficient friction is provided to position the lid just above the horizontal, then it will be needlessly difficult to move the lid when it is nearly vertical.